Early postoperative MRI findings following surgery for herniated lumbar disc part II: A gadolinium-enhanced study

Abstract

The aim of our study was to evaluate the contrast-enhanced MR imaging (MRI) findings, in the early postoperative period, in unselected patients undergoing lumbar microdiscectomy (15/16 had total resolution of their symptoms). Contrast-enhanced imaging studies were performed, in all 16 patients of our series, before surgery, and at the third postoperative day and, two months after surgery. Postoperative paraspinal muscles enhancement was present in all patients. In the postoperative period, nerve root enhancement was present in 5/16 patients at the early survey and persisted in one after two months. A pseudohernia depicted as epidural intermediate signal intensity tissue, was seen in 13 patients at the third day MRI, and only in eight after two months. This pseudohernia enhanced peripherally in 8/13 patients and enhanced homogeneously in the remaining five at the first postsurgical examination; in the late MRI the peripheral enhancement was appreciable in only two patients while a homogeneous enhancement was observed in six. Clinical symptoms resolved completely in 14/16 patients on clinical evaluation at the third postoperative day, while the remaining two patients showed residual symptoms and signs of radicular compression. At the early MRI these two patients showed intradural nerve root enhancement. Two months later, one patient did not show the previously described nerve root enhancement and improved clinically, while the other had a positive Straight Leg Raising Sign with persistent intradural nerve root enhancement. In conclusion, no correlation between clinical course and contrast-enhancement of pseudohernia and extradural nerve root was appreciable, although intradural nerve root enhancement seems to represent a clinically relevant finding.

Symptomatic Nerve Root Changes on Contrast-Enhanced MR Imaging after Surgery for Lumbar Disk Herniation

“…[23][24][25] NRE in the immediate postoperative period may be a normal finding. 3 This phenomenon has been reported in 29% to 62% of asymptomatic patients 3 to 6 weeks after surgery, and the incidence of NRE decreased by 3 months with no enhancement after 6 months.…”

Imaging and histopathologic features of reversible nerve root and peripheral nerve edema secondary to disc herniation in a cat

“…68 Similarly, in humans reversibility of these findings after decompressive surgery has been demonstrated. 69 The overall outcome in IVDH in cats is considered good to excellent after decompressive surgery, 1,35,36,41 but the relevance of concomitant thickening and contrast enhancement of the nerve or nerve root in cats is unknown. The cat described here showed complete neurological recovery and reversibility of nerve and nerve root changes on MRI within 4 months after surgery, suggesting that, similar to IVDH in dogs, thickening and increased contrast uptake of the nerve root may not be an indicator of negative outcome.…”

“…Thickening of the nerve root and contrast uptake have not been reported to influence outcome in dogs with IVDH 68 . Similarly, in humans reversibility of these findings after decompressive surgery has been demonstrated 69 . The overall outcome in IVDH in cats is considered good to excellent after decompressive surgery, 1,35,36,41 but the relevance of concomitant thickening and contrast enhancement of the nerve or nerve root in cats is unknown.…”

Postoperative computed tomography and low-field magnetic resonance imaging findings in dogs with degenerative lumbosacral stenosis treated by dorsal laminectomy

“…Postoperative evaluations included the same clinical, neurological, haematology, serum biochemistry, CT and MRI examinations as were used preoperatively. Examinations were performed at the earliest four months after the surgery in order to avoid imaging changes related to routine postoperative healing (11,16,19). The time of the postoperative evaluation was based on the time when the dog entered the study (dogs towards the end of the study had shorter follow-up times) and the availability of the dog owner and the dog.…”